The Am386 CPU was released by AMD in 1991. A 100%-compatible clone of the Intel 80386 design, it sold millions of units and positioned AMD as a legitimate competitor to Intel, rather than just a second source for Intel's x86 CPUs.
While the CPU was essentially ready to be released prior to 1991, Intel kept it tied up in court. AMD had previously been a second-source manufacturer of Intel's designs, and AMD's interpretation of the contract was that it covered all of them. Intel, however, claimed that the contract only covered the 80286 and prior processors. After a few years in the courtrooms, AMD finally won the case and the right to sell their Am386. This paved the way for competition in the CPU market and thus lowered the cost of owning a PC.